Hydraulic pump with by-pass flow



Dec. 29, 1953 HUBER 2,664,048

HYDRAULIC PUMP WITH BY-PASS FLOW Filed May.21, 1951 2 Shuts-Sheet l Fie. 1

INVENTOR. I

hewVJ. Huber .A'l'l'carneys Dec. 29, 1953 M. w. HUBER 2,564,048

HYDRAULIC PUMP WITH BY-PASS FLOW Filed May 21, 1951 2 Sheets-Sheet 2 FILE-3 2, 64' 33 K F T- m IN V EN TOR. Maiiheww. Huber BYQWQAHKM Patented Dec. 29, 1953 HYDRAULIC PUMP WITH BY-PASS FLOW Matthew W. Huber, Watertown, N. Y., assignor to The New YorkAir Brake Company, a corporation of New Jersey ApplicationMay 21, 1951, SerialNo. 227,331

(01. ins-:37)

15 Claims.

This invention relates to multiple delivery hyidraulic pumps, and particularly to pumps in which the main delivery is variable according to principles characteristic of the-patent to M. W. ,Huber 2,433,222, issuedDecember 23, 194.7.

The objects of the invention are several. One

is to assurea by-pass flow of liquid through the pump to provide cooling and lubrication, even whenthe pump is operating at or near zero delivery, and evenwhen the by-pass flow must be against a substantial pressure head.

An ancillary feature is the construction of the ;pump in such a Way as to permit delivery of bypassed liquid against head pressures which may be nearly as high .as the head pressure against Iwhich the main pump-delivery occurs, or alternatively may be much less.

A very important object is to ensure the minimum practicable power consumption when the pump operates at, or substantially at, zero do livery.

The by-passflow is delivered fromthe cylinders through ports in the cylinder wallwhichare exposed by the corresponding plungers near the ends of'each displacement stroke. Where the .by-pass flow encounters high back pressures check-valves control these ports to inhibit back ,flow. Theneed for this is particularly evident when the pump is operating at and near zero delivery, because then the spill-back. ports-tend itobe continuously open. However at normal operative speeds there are pronounced inertia effects that cause by-pass delivery to occur against :head pressures of considerable magnitude (several sures can be had in the absence of check-valves,

these valves will "be omitted, because in such casethere is protection against the generation of I destructive pressures. .Also the simpler construction is desirable.

If oneassume that a variable-delivery pump such as the patented pump, referred-to above, is

delivering into an absolutely tight line, one can imagine the pump moving to zero deliveryposi- 'tion and staying there, Absolutely tight lines being rarely encountered, because of seepage past valves-and similar losses, the fact is that the .pump controller often hunts in-a narrow range close to zero delivery position. Since it requires considerable force to start flow ,against ahead .2 of 3060 =p. s. .i. the plungers deliver impacts near the end of each stroke as their spill-backvalves close. These impacts deliver little or no oil but they do absorb considerable energy. Hence such a pump is likely to be characterized by undue energy consumption at its zero delivery.

Power consumption at and near zero delivery .is-minimized according to the present invention,

by causing a minority of the plungers, and preferably only one plunger to continue to deliverafter the pressure control has caused allthe others to cease to deliver. The active plunger maintains the head by displacing oil through a short but useful effective stroke while the othersarefreed from the recurrent loads which consume energy at rates out ,ofproportion to thenegligible quan tities of oil which th ey might deliver.

The result is secured by changing the dimensions of one spill-back sleeve, or the location of the port which it controls, so that in the zero delivery setting of the pump controller its ,spillback port closes or at anyrate nearlyclosesbut the ports of theother plungers remain open. A

somewhat similar by-pass arrangement is described and claimed inapplicants co-pendingapplication Serial No. 159,825, filed .May 3, 1950.

The present invention can be used with or without the by-pass. .When a byepass is provided it ensures that regardless of pump speed, one

plunger will deliver positively to the by-pass, as

well asto the pump discharge. Inpractioahowever they all deliver tothe by-pass becauseof inherent inertia effects.

.Assured by-pass circulation .for cooling and lubrication permits closer fitting of plungers.

Comparative tests of adequate duration show significant gains in volumetric efficiency, and a reduction of power consumption .at zero delivery to of-the amount heretofore considered minimum.

The pump so tested will now be described by reference to the accompanying drawing in which:

. Fig. 1 is a longitudinal axial section through the pump on a plane intersecting the axes of the inlet and discharge connections.

,Fig. 2 is a perspective view of the multiple check-valve which maybe used to control the 'bypass ports, ormay be omittedaltogether.

' Figs.3 to 7 inclusive are fragmentary sections showing plunger positions. In each, the fullfdelivery position of the spill-back valve isshown in full lines and the zero or minimum delivery position in broken lines.

Figs. 3, ,4 and .5 show the one plungerwhich the atypical .sleeve respectively at the start 3 of the displacement stroke, at closing of the inlet port and at the end of the displacement stroke. Figs. 6 and '1 show one of the eight plungers having regular or typical sleeves at the start and at the end of the displacement stroke.

The pump housing comprises a main body portion II and a cap I2. A threaded connection I3 for the main discharge line is formed in cap I2. A smaller threaded connection I4 for the bypass line is formed in body II. A fitting I5 is threaded at I6 into the entrance end of inlet passage I1 and sealed by gasket I8. Passage I1 leads directly to the swash plate chamber. The fitting I5 is threaded at I9 to receive the suction The by-pass connection I4 commonly would return by-passed liquid (oil) to the sump of the hydraulic system in which the pump is included, either directly or through some device to be lubricated and cooled. The connection I4 commonly would be and at any rate can be under substantial back-pressure. These details concern the system with which the pump is used and hence do not require elaboration. Whatever becomes of oil by-passed through connection I4, it assures continuous oil flow while the pump is running, so that oil continuously enters through passage I1 and flows in contact with the plunger-actuating mechanism.

The head I2 and body I are held together by threaded connections, not visible in the drawing and confine between them a generally cylindrical cylinder block 2| and a generally cylindrical guide block 22, which are fixed in assembled relation by conventional means including screws, one of which appears in broken lines at 23.

The illustrated pump has nine plungers 24. Consequently the block 2| has nine cylinders 25 and the guide block 22 has nine guide ways 26, each axially alined with a corresponding cylinder. The axes of the plungers are parallel and are uniformly spaced in circular arrangement around the axes of the cylindrical blocks 2| and 22 and also around the axis of the drive shaft-21.

Each cylinder 25 has an annular inlet port 28 fed by a passage 29 bored in cylinder block 2|. These lead from the spill-back valve-space 3| enclosed between the cylinder block 2| and the guide block 22 which is cup shaped. Passages 32 connect space 3| with passage I1.

To the left of port 28 each plunger 24 is guided in block 2| for a considerable distance, and formed in this guide portion is an annular bypass port 33, one for each plunger. A passage 34 leads from each port 33 to the bottom of an annular channel 35, flared outward in cross section as shown. Channel 35 communicates through a drilled port 36 with connection I4.

In channel 35 is a valve comprising a thin flexible strip 31 curled to circular form with its ends overlapping. The valve is contracted by an encircling garter spring 38 formed of a sinuous metal strip whose ends are hooked together at 39. The strip 31 functions as a plurality of check valves individually controlling passages 34. The

use of the parts 31, 38 is optional and depends on the performance desired. The size of ports 34 is also determined by the performance desired, particularly when parts 31, 38 are omitted.

The end of each cylinder 25 is closed by a discharge valve 4I which is urged to its seat on block 2| by a coil compression spring 42. The valves are housed in an annular space 43 between block 2| andcap I2, and connected with discharge connection I3 by passage 44. The cap I2 is formed so will deliver a small quantity through its 4 with seats for springs 42 and with a guide way for the axial stem of each valve as clearly shown in Fig. 1.

It is contemplated that space 43 will be maintained at high pressure, pressures of 3000 p. s. i. being everyday practice and pressures of at least 5000 p. s. i. being attainable. They will be used whenever apparatus to use them becomes available.

The block 2| is sealed to body II by toric gaskets 45 on opposite sides of channel 35 and to cap I by toric gasket 46 and filler ring 41. Pressure in space 43 forces the blocks 2 I, 22 against shoulder 48, so that they are positively positioned.

The means for positively reciprocating the plungers 24 forms the subject of Patent 2,620,738, issued December 9, 1952, subsequently to the filing of the present application and requires only brief description.

Shaft 21 drives swash plate 5| which is sustained by thrust bearing 52. Each plunger 24 has a hemispherical enlarged end 53 in which is socketed a universally tiltable slipper 54 and against which is seated a universally tiltable thrust ring 55. The slippers 54 engage the face of swash plate 5| and the rings 55 engage the plane face of a nutating plate 56. Plate 56 tilts on a hemispherical thrust journal 51 and has notches at its periphery to receive the necks of plungers 24 which pass freely therethrough.

The axes of tilt of each slipper and its related ring are coincident and the plane face of plate 56 engaged by the rings 55 passes through the axis of spherical journal 51. Any suitable geometrically similar reciprocating mechanism might be substituted, so far as the present invention is concerned.

Each plunger 24 has several radial by-pass ports 58 and several radial spill-back ports 59. Four of each have proved satisfactory and are illustrated.

Ports 58 are so located that they open into space 3| when their plungers are fully retracted (see Figs. 3 and 6) and are blanked by block 2| before the end of the plunger closes the inlet port 28 (see Fig. 4). Near and at the end of the displacement stroke they communicate with their corresponding by-pass ports 33 (see Figs. 5 and '1) Ports 59 are so located that in the fully retracted position of their plungers they communicate with space 3| (see Figs. 3 and 6). On their displacement strokes they are controlled by either the typical spill-back sleeve valve 6| of Figs. 6 and '1 or the atypical sleeve valve 62 of Figs. 3, 4 and 5. All the sleeve valves 6|, 62 are positioned by a spider 63 which engages the annular groove 64 in each valve.

The difference between typical valves and the atypical valve is simply that when the valves GI, 62 of Figs. 3 to '1 are in their dotted line positions (zero delivery setting) the typical valves 6| will close their ports 59 later in the stroke than does the atypical valve 62. The easiest way to attain this result (but not the only way) is to make the valve 62 longer than the valves 6| the extra length being at the left hand end of the valve as viewed in Figs. 3, 4 and 5.

As a consequence plungers having typical valves in zero delivery position will have their spill-back ports open until the by-pass ports open but any plunger having an atypical valve in its correspondin position will have its spill-back valve closed before its by-pass ports open, and

dis-

charge valve 4|.

Spider '63 is carried on the-endof piston "rod 65 which has a coaxial cylindrical enlargement -66. Parts 65, 66 extend through the cylinder bushing -61 sealed inblock 2| by toric gaskets, as shown. Pressure head in chamber-43 is ad- "mitted by choke 58 andpassaget to the space Within cylinder bushing 61 where it reacts to the right (as seen in Fig. l) on thediiierential 'area betweenparts 65 and tfi. 'Thespring seats ll, '12, T3. springs 16, 15, tie=bolt l 6,*adjustable slide -71 and adjusting screw '18 are l components of a known adjustable spring'loading assembly for biasing spider 53 to the left, as "viewed in Fig. 1.

In any reciprocating positive displacement pump operating at 3000 "R. P. and higher against head pressures of300'0 p.s. i. and higher, inertia eiiects on the liquid-are substantial and stresses developed-by-static pressures-are cyclical- -ly augmented by kinetic reactions about which little can be known except-that they are severe.

The thickness of the housing is limited by practical considerations, and-while the structure is rigid so farasis visible there must be some rather substantial deflections. -sional tolerances are a manufacturing necessity and some of these are cumulative, so that it is next to impossible to determine valve timing even from the actual :pump.

-Asa consequence, figures suchas-Figssdto 7 must'be considered as a basis of explanation of what-apparently happens, rather than as a demonstration of-the precise timing of ports.

A striking 'confirmationiof this is the circumstance that removalof valve i3! and its-spring 38 reduces the maximum headagainst which bypass fiowcan'be delivered, but.does not greatly reduce flow against :heads as :high as four or five hundred pounds per square inch. .It does inhibit generation of destructivepressures incase the by-pass path is closed.

Referring to Figs. 5.and 7 .it is .COIIVGRiBIltifOT purpose of explanation to say;thatnin;the-,aerodisplacement (broken linelposition :of atypical sleeve 5| flow tossstartsatleast as soon asflow through 59 ends whereas inthe corresponding position or" the atypical sleeve .52 :flow through 59 ends before flow to .33 can :start. .However there are inertia effects, :and just as :a little lead is beneficial in a distributing valve, .so is lead beneficial here. For any pump .anoptimum setting can :be determinedon a trial and error basis, .but exactly -what;.itis dimensionally has so far defied-attempts-atymeasurement.

Figs. 3 to '1 should not be..too .literallyfinterpreted'for they illustrate -;a principle rather than strict dimensional relations. and should be considered on that basis.

They demonstrate better thananyverbal description can, the fact that at and near the zero displacement setting the atypicalsleeve 6'2 alone .regulates, allowing the typical sleeves .6litoopen Moreover. dimen- They are offered 6 1.In a :pump, the combination/of :a plurality of cylinders; a plurality of'plungers, onereciprocable in-eachcylinder, each plunger :having in spill-back port; means for reciprocating said plungers; a discharge connection common .to said cylinders and in which a discharge pressure )is maintained by operationof the-pump; .a pressure motor subject to said'pressure; means for loading said motor in oppositiontosaid pressure; valves controllingsaid'spill-back ports'andshiftable in the direction of plunger reciprocation to vary the effective stroke of the corresponding plungers; and connections through which the motor shifts said valves in ranges of positionfiso differentiated that as to the majority of plungers the efiective stroke is varied in inverse relation to discharge pressure between amaximum and zero, and as to theminority, not less than one, the effective strokeis simultaneously-varied between a maximum and an efiective strokegreater than zero, whereby at least one cylinder remains effective to maintain discharge pressure against leakagewhen the remaining cylinders have, ceased delivery.

2. The combination defined in claiml in which said minority is one plunger, and the differentiation between the effective strokes of themajority and the effective stroke of said one is sufficient'to afford a precise control range near zero delivery inwhich control is efiected by varying the effective stroke of said one-plunger.

3. Thecombination defined in claim 1 in which the spill-back valves are sleeves through which the spill-back ported portion of the respective plungers reciprocate, each :sleeve havinga con- I "secondary discharge port controlled by "said plunger and opened thereby in each stroke atua time when positive displacement is occurring; and means for causing at least the liquid passing through said secondary discharge port to fiow in contact with said plunger-reciprocating means.

5. The combination defined in claim 4in which the means which varies the effective plunger stroke is of the type which delays in varying degree the commencement of positive displacement, and the secondary dischargeport is arranged to be opened by the plunger near the end of its displacing stroke.

'6. A multi-cylinder'pump comprising-in com- "bination'a plurality of cylinders having inlet ports and a suction connection common thereto; plungers, one reciprocable in each cylinder; discharge valves one for each cylinder; a main dis charge connection into which all said discharge valves deliver, the pressure in said connection serving to bias said valves in their closing directions; means for reciprocating said plungers; means common to all said plungers and adjustable to vary the effective stroke thereof between full stroke and minimum efiective stroke, in all of which adjustments positive displacement by a minority comprising at least one plunger occurs; means afiording secondary discharge ports for the various cylinders, controlled by respective plungers and so arranged that each is open during part of the minimum effective stroke of its plunger; and means for passing at least that liquid which flows through the secondary discharge ports in contact with said plunger reciprocating means.

7. The combination defined in claim 6 in which the means adjustable to vary the efiective strokes of the plungers are so contrived that the majority of said plungers have their strokes simultaneously varied between full and zero effective stroke and said minority between full and a minimum efiective stroke greater than zero.

8. The combination defined in claim 6 in which the means adjustable to vary the efiective strokes of the plungers are so contrived that the majority of said plungers have their strokes simultaneously varied between full and zero eilective stroke and said minority between full and a minimum effective stroke greater than zero within a part of which minimum said secondary discharge ports are open.

9. The combination with the structure defined in claim 6 of check valve means serving to inhibit back flow through said secondary discharge ports.

10. In a hydraulic displacement pump unit the combination of means enclosing a working space having an inlet port adapted to be controlled by a plunger, a discharge port and a guide way coaxial with said working space; a plunger reciprocable in and filling said guide way with its end so positioned in said working space that when moved in a displacing direction it first closes said inlet port and then displaces hydraulic liquid through said discharge port; a spring-loaded pressure actuated valve controlling said discharge port; secondary discharge means comprising ports respectively in said plunger and in said guide way positioned to communicate as the plunger approaches the end of its displacing stroke; spill-back means including a port leading through the plunger from said working space and an adjustable spill-back valve controlling said port to close the same through variable portions of the displacement stroke; means for adjusting the spill-back valve; and means for reciprocating said plunger.

11. The combination defined in claim 10 in which the secondary discharge means, and the spill-back means are so coordinated that when the secondary discharge means are open the spillback means are closed.

12. A pump comprising a plurality of units as defined in claim 10 with single means for adjusting the spill-back valves and single means for reciprocating the plungers each common to all units, the majority of said units having their spill-back and secondary discharge means so coordinated that in zero discharge position both are open simultaneously; the minority of said 8 units, not less than one being characterized by a different coordination such that when the secondary discharge means are open the spill-back means are closed even when adjusted for minimum delivery.

13. In a hydraulic displacement pump unit the combination of means enclosing a working space having an inlet port adapted to be controlled by a plunger, a discharge port and a guide way coaxial with said working space; a. plunger reciprocable in and filling said guideway with its end so positioned in said working space that when moved in a displacing direction it first closes said inlet port and then displaces hydraulic liquid through said discharge port; a spring-loaded pressure-actuated valve controlling said discharge port; secondary discharge means comprising ports respectively in said plunger and in said guide way positioned to communicate as the plunger approaches the end of its displacing stroke; check valve means inhibiting back flow through said secondary discharge means; spill-back means including a port leading through the plunger from said working space and an adjustable spill-back valve controlling said port to close the same through variable portions of the displacement stroke; means for adjusting the spill-back valve; and means for reciprocating said plunger.

14. In a hydraulic pump, the combination of a cylinder having an inlet port, a main discharge port and a secondary discharge port; a plunger reciprocable in said cylinder and controlling said inlet port, said plunger obstructing said secondary discharge port through a first and major portion of its displacement stroke and having a port which thereafter connects the cylinder and secondary discharge port through a minor portion of the displacement stroke to afford brief periodic discharges through said secondary port; a pressure-actuated valve controlling flow through the main discharge port, said valve being biased in a closing direction by the pressure against which the pump discharges and being capable of being opened by pressure in said working space when said pressure is dominant; and adjustable means associated with the plunger for neutralizing the displacing action of said plunger through variable portions of its displacement stroke within the aforesaid major portion thereof.

15. The combination of the structure defined in claim 14 with one way flow means controlling said secondary discharge port and inhibiting back flow therethrough.

MATTHEW W. HUBER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,223,759 Dillstrom Dec. 3, 1940 2,436,797 Deschamps et al. Mar. 2, 1948 2,512,799 Huber June 2'7, 1950 

